Unexpected high prevalence of IgG-antibodies to hepatitis E virus in Swedish pig farmers and controls

Hepatitis E virus (HEV) infections are responsible for large waterborne outbreaks in developing countries. Sporadic cases in the developed world are mainly imported via immigrants and travellers from endemic areas. HEV has been suggested to be a zoonotic infection where pigs may be an important reservoir for the disease and specific swine strains of HEV have been identified which can infect also humans. The aim of this study was to analyse if Swedish pig farmers are more exposed to HEV than persons with other occupations. A total of 115 male pig farmers aged 40-60 y and 108 age- and geographically-matched control subjects were tested for IgG anti-HEV antibodies. No statistical difference in anti-HEV prevalence was noted between pig farmers (13.0%) and control subjects (9.3%). The prevalence of anti-HEV antibodies in the pig farmers and controls was higher than that previously reported among other populations in Europe (< 1-9%). Further studies are needed to elucidate the routes for infection of indigenous HEV and if sub-clinical infections with pig associated HEV strains occur in Sweden.